Method of processing quantum dot inks

ABSTRACT

A method of storing and transporting quantum dot formulations is provided. The method includes storing and/or transporting the quantum dot formulation under an oxygen-containing atmosphere. A sparged and degassed quantum dot formulation is also described.

This application is a continuation of International Application No.PCT/US2013/025235, filed 7 Feb. 2013, which was published in the Englishlanguage as International Publication No. WO 2013/122820 on 22 Aug.2013, which International Application claims priority to U.S.Provisional Patent Application No. 61/599,216, filed on 15 Feb. 2012.Each of the foregoing is hereby incorporated herein by reference in itsentirety for all purposes.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the technical field of quantum dots,including methods, and compositions and products including quantum dots.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present disclosure are directed to quantum dotformulations, containers including quantum dot formulations, and relatedmethods, including methods relating to the storage and/or transport ofsuch quantum dot formulations. Embodiments of the present disclosure arealso directed to the processing of quantum dot formulations that havebeen stored or transported for a period of time.

Quantum dots may perform less efficient under operating conditions ofheat and light flux if in an environment that includes oxygen.Accordingly, quantum dots should be maintained in a substantiallyoxygen-free environment. According to aspects of the present disclosure,a quantum dot formulation can be stored or transported under an oxygenenvironment, and then the oxygen can be removed before the formulationis placed into the vessel or tube or container, without loss inefficiency or reliability.

According to one aspect, oxygen is included into a quantum dotformulation. According to one aspect, an effective amount of oxygen isincluded into a quantum dot formulation. According to an additionalaspect, oxygen is included into a quantum dot formulation by passingoxygen over a surface of the quantum dot formulation. According to yetan additional aspect, oxygen is included into a quantum dot formulationby passing oxygen through the quantum dot formulation, such as byinjecting oxygen into or bubbling oxygen through the quantum dotformulation. According to an additional aspect, oxygen is included intoa quantum dot formulation by mixing oxygen into the quantum dotformulation. According to an additional aspect, oxygen is included intoa quantum dot formulation by placing the quantum dot formulation underan atmosphere that includes oxygen. According to one aspect, oxygen isincluded in the quantum dot formulation by diffusion. According to anadditional aspect, the quantum dot formulation may be agitated or mixedor stirred such that oxygen in the oxygen containing atmosphere isincluded in the quantum dot formulation. According to one aspect, aquantum dot formulation is placed within a container under an atmospherethat includes oxygen.

According to one aspect, oxygen is included into a quantum dotformulation in an amount effective to inhibit polymerization ofpolymerizable species in the quantum dot formulation. According to oneaspect, oxygen is included into a quantum dot formulation in an amounteffective to scavenge free radicals. According to one aspect, oxygen isincluded into a quantum dot formulation in an amount effective toscavenge free radicals and to inhibit polymerization of polymerizablespecies in the quantum dot formulation through free radicalpolymerization. According to one aspect, oxygen is included into aquantum dot formulation in an amount effective to reduce the amount offree radicals within the quantum dot formulation.

According to one aspect, the quantum dot formulation includes aninhibitor compound or polymerization inhibitor compound which may alsobe referred to as an inhibitor. The inhibitor compound when in thepresence of oxygen inhibits inadvertent or undesired polymerization ofpolymerizable species in the quantum dot formulation. The inhibitorcompound when in the presence of oxygen inhibits, and preferablyprevents, the polymerizable species in the quantum dot formulation frominadvertent or undesired polymerization. Accordingly, oxygen is includedin the quantum dot formulation in an amount relative to the inhibitorcompound. According to one aspect, oxygen is included in the quantum dotformulation in an amount effective to scavenge free radicals and reactwith the inhibitor compound thereby removing the free radical from thequantum dot formulation. According to one aspect, oxygen is supplementedto the quantum dot formulation over a period of time to provide aneffective or sufficient amount of oxygen to scavenge free radicals fromthe quantum dot formulation and react with the inhibitor compoundthereby removing free radicals from the quantum dot formulation.

Optionally, the quantum dot formulation may be placed under conditionsof no light or low light or light of certain wavelength. In particular,these light conditions would not include wavelengths of light thatactivate any photoinitiators that may be included in the inkformulation. As the shelf life of the ink is shortened as the storagetemperature is raised, elevated storage or transportation temperaturesshould be avoided. According to one aspect, the quantum dot formulationis placed into an opaque container which excludes or substantiallyexcludes light from entering the container. According to one aspect, thequantum dot formulation is placed under conditions that excludewavelengths of light, such as an opaque container or light filteringcontainer, that activate photoinitiators that may be present in thequantum dot formulation. According to one aspect, the quantum dotformulation is placed under conditions absent of light having awavelength of about 500 nm or less, such as about 450 nm or less.Optionally, the quantum dot formulation may be placed in an environmentwhere the temperature is insufficient to polymerize polymerizablespecies in the quantum dot formulation. According to one aspect, thequantum dot formulation may be kept or maintained at a temperature ofroom temperature or less, such that polymerization does not occur.According to one aspect, the quantum dot formulation may be kept ormaintained at a temperature of between about 4° C. and 25° C. Accordingto one aspect, the quantum dot formulation may be kept or maintained ata temperature of room temperature or less. According to one aspect, thequantum dot formulation may be kept or maintained at a temperature ofbetween about 4° C. and 15° C. According to one aspect, the quantum dotformulation may be kept or maintained at a temperature of roomtemperature or less. According to one aspect, the quantum dotformulation may be kept or maintained at a temperature of between about20° C. and 25° C. Optionally, the quantum dot formulation may be placedin an environment where the temperature is less than about 23° C.

The quantum dot formulation including oxygen therein may be placedwithin a container, such as an opaque container, and remains within thecontainer for a period of time until use of the quantum dot formulationis desired. The quantum dot formulation may be placed within acontainer, such as an opaque container under an atmosphere that includesoxygen and remains within the container for a period of time until useof the quantum dot formulation is desired. The quantum dot formulationincluding oxygen therein may be placed within a container, such as anopaque container, under an atmosphere that includes oxygen and remainswithin the container for a period of time until use of the quantum dotformulation is desired. Such a period of time includes a storage time.Such a period of time includes a shipping time. Accordingly, aspects ofthe present disclosure include methods of storing a quantum dotformulation including placing a quantum dot formulation including oxygentherein within a container, such as an opaque container, and storing thecontainer for a period of time. Accordingly, aspects of the presentdisclosure include methods of storing a quantum dot formulationincluding placing a quantum dot formulation within a container, such asan opaque container, under an atmosphere that includes oxygen andstoring the container for a period of time. Accordingly, aspects of thepresent disclosure include methods of storing a quantum dot formulationincluding placing a quantum dot formulation including oxygen thereinwithin a container, such as an opaque container, under an atmospherethat includes oxygen and storing the container for a period of time.

Aspects of the present disclosure include methods of shipping a quantumdot formulation including placing a quantum dot formulation includingoxygen therein within a container, such as an opaque container, andshipping the container from one location to another. Aspects of thepresent disclosure include methods of shipping a quantum dot formulationincluding placing a quantum dot formulation within a container, such asan opaque container, under an atmosphere that includes oxygen andshipping the container from one location to another. Aspects of thepresent disclosure include methods of shipping a quantum dot formulationincluding placing a quantum dot formulation including oxygen thereinwithin a container, such as an opaque container, under an atmospherethat includes oxygen and shipping the container from one location toanother. Methods of storing or shipping described herein may alsoinclude either storing or shipping the container of the quantum dotformulation under light conditions or temperatures described herein.Aspects of the present disclosure are further directed to a container,such as an opaque container, including a quantum dot formulation havingoxygen therein. Aspects of the present disclosure are further directedto a container, such as an opaque container, including a quantum dotformulation under an atmosphere that includes oxygen. Aspects of thepresent disclosure are further directed to a container, such as anopaque container, including a quantum dot formulation having oxygentherein and under an atmosphere that includes oxygen.

Aspects of the present disclosure also include methods of processingquantum dot formulations including oxygen therein and/or that have beenplaced under an atmosphere that includes oxygen. According to oneaspect, all or substantially all oxygen is removed from the quantum dotformulation such that that there is no or substantially no dissolved orentrapped oxygen in the quantum dot formulation. According to oneaspect, all or substantially all gas is removed from the quantum dotformulation such that there is not dissolved or entrapped gas in thequantum dot formulation. According to one aspect, all or substantiallyall oxygen is removed from the quantum dot formulation when all orsubstantially all gas is removed from the quantum dot formulation.Accordingly, a method is provided for removing all or substantially allgas from a quantum dot formulation. Methods of removing all orsubstantially all gas from a liquid formulation are known to those ofskill in the art. Such methods may be referred to as degassing.

According to one aspect, the quantum dot formulation is subjected to aninert gas such that oxygen is removed from the quantum dot formulation.According to one aspect, an inert gas is introduced into the quantum dotformulation, such as by spraying, bubbling, the gas through the quantumdot formulation. According to one aspect, the quantum dot formulation issparged with an inert gas. According to one aspect, the quantum dotformulation is degassed of oxygen by the inert gas. According to oneaspect, the quantum dot formulation is sparged or inert gas is otherwiseadded to the quantum dot formulation to the extent sufficient to removesubstantially all oxygen from the quantum dot formulation. According toan additional aspect, the quantum dot formulation is degassed to theextent sufficient to remove substantially all gas, whether oxygen ornot, from the quantum dot formulation. Accordingly, aspects of thepresent disclosure are directed to a degassed quantum dot formulation.Accordingly, aspects of the present disclosure are directed to a spargedquantum dot formulation. Accordingly, aspects of the present disclosureare directed to a deoxygenated quantum dot formulation. Accordingly,aspects of the present disclosure are directed to a sparged and degassedquantum dot formulation. The sparged quantum dot formulation includes noor substantially no oxygen. The degassed quantum dot formulationincludes no or substantially no gas. The degassed quantum dotformulation includes no or substantially no oxygen. The sparged and/ordegassed quantum dot formulation may be maintained under an inertatmosphere or under vacuum prior to use.

According to one aspect, the sparged and/or degassed quantum dotformulation is used in devices known to those of skill in the art wherelight emission from quantum dots is desired. Such devices include remotedownconversion optics such as those for solid state lighting, LCDdisplay backlight units, solar energy devices and the like; on-chipapplications such as LED downconversion to replace or enhance phosphordownconversion.

As an example, a sparged and/or degassed and/or deoxygenated quantum dotformulation which includes no or substantially no oxygen and/or no orsubstantially no gas can be used in the manufacture of an opticalcomponent or other material, such as a quantum dot film which is to beused with a device where light emission from quantum dots is desired.According to a certain aspect, the sparged and/or degassed quantum dotformulation is introduced into a vessel or tube or container to be usedan optical component. According to one aspect, the sparged and/ordegassed quantum dot formulation is introduced into the vessel or tubeor container and the vessel or tube or container is then sealed.According to one aspect, the quantum dot formulation within the vesselor tube or container is under oxygen-free conditions such as a vacuum.Methods of introducing a quantum dot formulation into a vessel or tubeor container are known to those of skill in the art and will be readilyapparent based on the present disclosure. According to a certain aspect,the quantum dot formulation within the vessel or tube or container isthen subjected to conditions to cure the quantum dot formulation into amatrix. An optical component including a polymerized quantumdot-containing formulation may then be used in various devices,including but not limited to those described herein.

According to one aspect, the sparged and/or degassed quantum dotformulation is used in the manufacture of a quantum dot film. Accordingto a certain aspect, the sparged and/or degassed quantum dot formulationis introduced into a composition used to make quantum dot film. Thecomposition is then subjected to processing conditions to manufacture afilm with quantum dots therein. Methods of making quantum dot films areknown to those of skill in the art and will be readily apparent based onthe present disclosure.

According to one aspect, the quantum dot formulation may be acombination of certain quantum dots, such as quantum dots that emitgreen light wavelengths and quantum dots that emit red lightwavelengths, and that are stimulated by an LED emitting blue lightwavelengths resulting in the generation of trichromatic white light.According to one aspect, the quantum dots are contained within anoptical component such as a tube or a film which receives light from anLED. Light generated by the quantum dots may be delivered via a lightguide for use with display units. According to certain aspects, lightgenerated by quantum dots, such as trichromatic white light, is used incombination with a liquid crystal display (LCD) unit or other opticaldisplay unit, such as a display back light unit. One implementation ofthe present invention is a combination of the quantum dots within a tubethe contents of which may be under oxygen-free conditions, an LED bluelight source and a light guide for use as a backlight unit which can befurther used, for example, with an LCD unit.

Optical components that include quantum dots according to the presentinvention include vessels, tubes or containers of variousconfigurations, such as length, width, wall thickness, andcross-sectional configuration. The term “tube” as used in the presentdisclosure includes a capillary, and the term “tube” and “capillary” areused interchangeably. Tubes of the present invention are generallyconsidered light transmissive such that light can pass through the wallof the tube and contact the quantum dots contained therein therebycausing the quantum dots to emit light. According to certain aspects,tubes may be configured to avoid, resist or inhibit cracking due tostresses placed on the tube from polymerizing a matrix therein orheating the tube with the polymerized matrix therein. In this aspect,the tubes of the present invention are glass tubes for use with quantumdots. Such tubes can have configurations known to those of skill in theart. Such tubes may have a stress-resistant configuration and exhibitadvantageous stress-resistant properties. The tube containing thequantum dots is also referred to herein as an optical component. Anoptical component can be included as part of a display device.

According to one aspect, the vessel, tube or container of the presentdisclose is made from a transparent material and has a hollow interior.Quantum dots reside within the tube and may be contained within apolymerized matrix material which is light transmissive. A polymerizablecomposition including quantum dots and at least monomers can beintroduced into the tube such as under oxygen free conditions. The tubemay be sealed to maintain the oxygen-free nature of the polymerizablecomposition. The polymerizable composition is then polymerized withinthe tube using light or heat, for example.

Accordingly, the present disclosure provides a tube including a spargedand/or degassed quantum dot formulation therein wherein the quantum dotformulation includes no or substantially no oxygen and/or no orsubstantially no gas. The present disclosure provides a tube including asparged and/or degassed and polymerized quantum dot formulation therein.The present disclosure provides a combination including a glass tubehaving a sparged and/or degassed and polymerized quantum dot formulationtherein; one or more light sources adjacent to the glass tube; and alight guide adjacent to the glass tube. The present disclosure providesa back light display unit including one or more light sources; a glasstube having a sparged and/or degassed and polymerized quantum dotformulation therein adjacent the one or more light sources; a lightguide interconnecting the glass tube and a display. The presentdisclosure provides a method for making an optical component comprisingintroducing a sparged and/or degassed formulation including quantum dotsinto a glass tube and polymerizing the polymerizable formulation to forma matrix including quantum dots.

Embodiments of the present invention are directed to the mixtures orcombinations or ratios of quantum dots that are used to achieve certaindesired radiation output. Such quantum dots can emit red and green lightof certain wavelength when exposed to a suitable stimulus. Still furtherembodiments are directed to various formulations including quantum dotswhich are used in various light emitting applications. Formulationsincluding quantum dots may also be referred to herein as “quantum dotformulations” or “optical materials”. For example, quantum dotformulations can take the form of flowable, polymerizable fluids,commonly known as quantum dot inks, that are introduced into the tubeand then polymerized to form a quantum dot matrix. According to certainaspects, quantum dot formulations can take the form of flowable,polymerizable fluids, commonly known as quantum dot inks, that areintroduced into the tube under oxygen-free conditions and thenpolymerized to form a quantum dot matrix. The tube is then used incombination with a light guide, for example. Such formulations includequantum dots and a polymerizable composition such as a monomer or anoligomer or a polymer capable of further polymerizing. Additionalcomponents include at least one or more of a crosslinking agent, ascattering agent, a rheology modifier, a filler, a photoinitiator, and apolymerization inhibitor compound which may be referred to as aninhibitor and other components useful in producing a polymerizablematrix containing quantum dots. Polymerizable compositions of thepresent invention include those that avoid yellowing when in the form ofa polymerized matrix containing quantum dots. Yellowing leads to alowering of optical performance by absorbing light emitted by thequantum dots and light emitted by the LED which can lead to a shift inthe color point.

Embodiments of the present invention are still further directed tovarious backlight unit designs including the quantum dot-containingtubes, LEDs, and light guides for the efficient transfer of thegenerated light to and through the light guide for use in liquid crystaldisplays. According to certain aspects, methods and devices are providedfor the illumination and stimulation of quantum dots within tubes andthe efficient coupling or directing of resultant radiation to andthrough a light guide.

Embodiments are further provided for a display including an opticalcomponent taught herein.

Embodiments are still further provided for a device (e.g., but notlimited to, a light-emitting device) including an optical componenttaught herein.

Each of the claims set forth at the end of the present application arehereby incorporated into this Summary section by reference in itsentirety.

The foregoing, and other aspects and embodiments described herein allconstitute embodiments of the present invention.

It should be appreciated by those persons having ordinary skill in theart(s) to which the present invention relates that any of the featuresdescribed herein in respect of any particular aspect and/or embodimentof the present invention can be combined with one or more of any of theother features of any other aspects and/or embodiments of the presentinvention described herein, with modifications as appropriate to ensurecompatibility of the combinations. Such combinations are considered tobe part of the present invention contemplated by this disclosure.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention as claimed. Other embodimentswill be apparent to those skilled in the art from consideration of thespecification and practice of the invention disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a flow chart describing a capillary fill procedure.

FIG. 2 is a graph of lumens over time.

FIG. 3 is a graph of CIE_(x) over time.

FIG. 4 is a graph of CIE_(y) over time.

The attached figures are simplified representations presented forpurposes of illustration only; the actual structures may differ innumerous respects, including, e.g., relative scale, etc.

For a better understanding to the present invention, together with otheradvantages and capabilities thereof, reference is made to the followingdisclosure and appended claims in connection with the above-describeddrawings.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention are directed to methods of storingquantum dot formulations. Quantum dot formulations are known to those ofskill in the art and include quantum dots within a polymerizableformulation. According to one aspect, quantum dot formulations are madeby combining quantum dots with a liquid formulation to produce aflowable formulation. Such flowable formulations may be referred to asquantum dot inks. Such quantum dot formulations may be made under aninert atmosphere, i.e. one lacking oxygen, as the presence of oxygen maybe disadvantageous insofar as ingredients of the quantum dotformulation, such as the quantum dots themselves, may react with oxygenor oxygen may otherwise detrimentally affect the performance of thequantum dots. For example, the presence of oxygen may lead tophoto-oxidation of the quantum dots under operating conditions ofelevated temperature and light flux. Due to oxygen sensitivity, oxygenis often eliminated during the quantum dot formulation manufacturingprocess, which results in the quantum dot formulation being under aninert atmosphere or a vacuum. Alternatively, quantum dot formulationscan be manufactured under an atmosphere including oxygen. However,oxygen may be removed before the quantum dot formulation is used, forexample, in an optical component, light device, display, or otherend-use application.

According to aspects of the present disclosure, oxygen is included intoquantum dot formulations. According to aspect of the present disclosure,quantum dot formulations are subjected to an atmosphere including oxygenwherein oxygen is introduced into quantum dot formulation. Such anatmosphere including oxygen can be referred to as an “oxygen-containingatmosphere.” According to one aspect, the oxygen-containing atmospherecan be air, such as ambient air. According to an additional aspect, theamount of oxygen in the oxygen-containing atmosphere should be at leastabout 1% to about 100% of the oxygen containing atmosphere. According toan additional aspect, the amount of oxygen in the oxygen-containingatmosphere should be at least about 5% to about 21% of the oxygencontaining atmosphere. Gases in the oxygen-containing atmosphere may beone or more inert gases. According to one aspect, the oxygen-containingatmosphere is moisture free or substantially moisture free.

For example, oxygen is included in a quantum dot formulation if thequantum dot formulation is to be stored for an indefinite period of timeprior to use or if the quantum dot formulation is to be transported froma first location to a second location. For example, quantum dotformulations are placed under an atmosphere including oxygen if thequantum dot formulation is to be stored for an indefinite period of timeprior to use or if the quantum dot formulation is to be transported froma first location to a second location. For example, oxygen is includedin a quantum dot formulation and the quantum dot formulation is placedunder an atmosphere including oxygen if the quantum dot formulation isto be stored for an indefinite period of time prior to use or if thequantum dot formulation is to be transported from a first location to asecond location. According to one aspect, the quantum dot formulationmay be maintained under an oxygen-containing atmosphere for the shelflife of one or more polymerizable compounds within the quantum dotformulation, such as one year from the date of manufacture of the one ormore polymerizable compounds.

According to one aspect, oxygen is included in the quantum dotformulation by handling the quantum dot formulation in air, e.g., bytransferring the formulation into a container in air. According to oneaspect, oxygen is mixed into the quantum dot formulation such as todissolve oxygen in the quantum dot formulation and/or the quantum dotformulation is placed under an atmosphere including oxygen. According toone aspect, the amount of oxygen in the oxygen-containing atmosphere orotherwise dissolved within the quantum dot formulation is sufficient toinhibit, and preferably prevent, undesired reaction or polymerization ofthe reactive or polymerizable compounds within the quantum dotformulation.

According to one aspect, the quantum dot formulation includes aninhibitor compound which inhibits undesired polymerization of thequantum dot formulation which may otherwise occur over time aftermanufacture of the formulation. Without wishing to be bound byscientific theory, oxygen present in the quantum dot formulationscavenges free radicals thereby inhibiting undesired free radicalpolymerization of the polymerizable compounds in the quantum dotformulation. Accordingly, oxygen is included in the quantum dotformulation in an amount sufficient to scavenge free radicals andinhibit free radical polymerization of the polymerizable compounds inthe quantum dot formulation. Without wishing to be bound by scientifictheory, oxygen present in the quantum dot formulation scavenges freeradicals and then reacts with the inhibitor compounds thereby removingfree radicals from the quantum dot formulation and inhibiting undesiredfree radical polymerization of the polymerizable compounds in thequantum dot formulation. Accordingly, oxygen is included in the quantumdot formulation in an amount relative to the inhibitor compound.According to one aspect, oxygen is included in the quantum dotformulation in an amount effective to scavenge free radicals and reactwith the inhibitor compound thereby removing the free radical from thequantum dot formulation. According to one aspect, oxygen is supplementedto the quantum dot formulation over a period of time to provide aneffective or sufficient amount of oxygen to scavenge free radicals fromthe quantum dot formulation and react with the inhibitor compoundthereby removing free radicals from the quantum dot formulation.

Accordingly, methods are provided for maintaining a quantum dotformulation during storage by subjecting the quantum dot formulation toan oxygen-containing atmosphere or otherwise dissolving oxygen in thequantum dot formulation and inhibiting reaction or polymerization ofreactive or polymerizable compounds within the quantum dot formulation.According to one aspect, the quantum dot formulation is protectedagainst undesired reaction or polymerization of reactive orpolymerizable compounds within the quantum dot formulation duringstorage. Methods are further provided for maintaining a quantum dotformulation during transportation from a first location to a secondlocation by subjecting the quantum dot formulation to anoxygen-containing atmosphere or otherwise dissolving oxygen in thequantum dot formulation and then transporting the quantum dotformulation. According to one aspect, the quantum dot formulation isprotected against undesired reaction or polymerization of reactive orpolymerizable compounds within the quantum dot formulation duringtransportation.

According to certain aspects, a quantum dot formulation is introducedinto a container, oxygen is dissolved in the quantum dot formulation andthe quantum dot formulation is subjected to an oxygen-containingatmosphere and the container is closed or otherwise sealed therebypreventing the quantum dot formulation from exiting the container andthereby maintaining the quantum dot formulation under anoxygen-containing atmosphere until use of the quantum dot formulation isdesired. Oxygen can be added to the quantum dot formulation by bubblingoxygen through the quantum dot formulation. Oxygen can be added to thequantum dot formulation by agitating, stirring or mixing the quantum dotformulation while under an oxygen containing atmosphere in a manner todissolve oxygen in the quantum dot formulation. Oxygen can be added tothe quantum dot formulation by placing the quantum dot formulation underan oxygen-containing atmosphere and allowing the oxygen to diffuse intothe quantum dot formulation.

According to one aspect, a quantum dot formulation having oxygendissolved therein is provided. According to one aspect, a container isprovided which includes a quantum dot formulation subject to anoxygen-containing atmosphere. According to one aspect, a container isprovided which includes a quantum dot formulation having oxygendissolved, therein. According to one aspect, a container is providedwhich includes a quantum dot formulation having oxygen dissolved thereinand which is subject to an oxygen-containing atmosphere. According toone aspect, a quantum dot formulation is transferred under an oxygencontaining atmosphere, such as by pouring or pipetting, to a container.The container is maintained under an oxygen-containing atmosphere andthe container is sealed.

According to additional aspects of the present disclosure, a quantum dotformulation including dissolved oxygen and which is maintained under anoxygen containing atmosphere is then processed for use. According to oneaspect, oxygen within the quantum dot formulation is removed. Exemplarymethods of removing oxygen from a quantum dot formulation includeintroducing an inert gas into the quantum dot formulation for a periodof time sufficient to remove the dissolved oxygen from the quantum dotformulation. Exemplary methods of removing oxygen from a quantum dotformulation include sparging. Sparging is a process well known to thoseof skill in the art and includes flushing or bubbling or otherwisesubjecting the quantum dot formulation to an inert or sparging gas suchthat dissolved oxygen is removed from the quantum dot formulation.According to one aspect, the sparged quantum dot formulation includes noor substantially no oxygen. According to one aspect, a sparged quantumdot formulation is provided. According to one aspect, the inert gas isnitrogen, helium, neon, argon, krypton, xenon, radon or other inert gas.Sparging can be carried out by simply bubbling inert gas through thequantum dot formulation for a period of time sufficient to purge thequantum dot formulation of oxygen.

According to an additional aspect, gas within the quantum dotformulation is removed. The gas can be oxygen or it can be any other gaspresent within the quantum dot formulation. Gas can be present withinthe quantum dot formulation by dissolving oxygen within the quantum dotformulation. Gas can be present within the quantum dot formulation bysparging the quantum dot formulation with a sparging gas, such as aninert gas. Methods of degassing a fluid are well known to those of skillin the art and include sparging with a different gas, heating andfiltering and vacuum degassing. Vacuum degassing can be carried out bysubjecting the quantum dot formulation to a vacuum to draw off theoxygen from within the quantum dot formulation. The quantum dotformulation can be agitated or mixed or recirculated under vacuum topromote the removal of dissolved oxygen. Other degassing methods existincluding sonication and membrane degassing. Quantum dot formulationswhich have been degassed include no or substantially no oxygen. Quantumdot formulations which have been degassed include no or substantially nogases. According to one aspect, a degassed quantum dot formulation isprovided.

According to one aspect, a quantum dot formulation including oxygen maybe subjected to both sparging and degassing. The quantum dot formulationmay be sparged to remove the oxygen from the quantum dot formulation andthen the sparged quantum dot formulation may be degassed, such as byvacuum, to remove gas from within the quantum dot formulation.Accordingly, the present disclosure includes a quantum dot formulationwhich has been sparged and degassed. According to one aspect, a spargedand degassed quantum dot formulation is provided.

According to one aspect, a sparged and/or degassed quantum dotformulation is introduced into a vessel, tube or container to create anoptical component or is otherwise included into a formulation used tomake a quantum dot film. The quantum dot formulation is subject toconditions which promote polymerization of the polymerizable materialsinto a polymer matrix including the quantum dot. According to certainaspects of the present disclosure, a vessel in the shape of a tube isprovided which includes quantum dots under oxygen-free conditions. Thetube is hollow and can be fashioned from various light transmissivematerials including glass.

According to one aspect, one or both ends of the glass tube may besealed. The seal can be of any size or length. One exemplary dimensionis that the distance from the end of the capillary to the beginning ofthe optically active area is between about 2 mm to about 8 mm, withabout 3 mm or 5 mm being exemplary. Sealing methods and materials areknown to those of skill in the art and include glass seal, epoxy,silicone, acrylic, light or heat curable polymers and metal. Acommercially available sealing material is CERASOLZER available from MBRElectronics GmbH (Switzerland). Suitable metals or metal solders usefulas sealing materials to provide a hermetic seal and good glass adhesioninclude indium, indium tin, and indium tin and bismuth alloys, as wellas eutetics of tin and bismuth. One exemplary solder includes indium#316 alloy commercially available from McMaster-Carr. Sealing usingsolders may be accomplished using conventional soldering irons orultrasonic soldering baths known to those of skill in the art.Ultrasonic methods provide fluxless sealing using indium solder inparticular. Seals include caps of the sealing materials havingdimensions suitable to fit over and be secured to an end of the tube.According to one embodiment, one end of the tube is sealed with glassand the other end is sealed with epoxy. According to one aspect, theglass tube with a quantum dot matrix therein is hermetically sealed.Examples of sealing techniques include but are not limited to, (1)contacting an open end of a tube with an epoxy, (2) drawing the epoxyinto the open end due to shrinkage action of a curing resin, or (3)covering the open end with a glass adhering metal such as a glassadhering solder or other glass adhering material, and (4) melting theopen end by heating the glass above the melting point of the glass andpinching the walls together to close the opening to form a molten glasshermetic seal.

In certain embodiments, for example, a tube is filled with a sparged anddegassed liquid quantum dot formulation under oxygen free conditions,the end or ends of the tube are sealed under oxygen-free conditions andthe liquid quantum dot formulation is UV cured. Tubes for containingquantum dot formulations for the manufacture of optical components canbe selected based on the intended end-use application. An oxygen-freecondition refers to a condition or an atmosphere where oxygen issubstantially or completely absent. An oxygen-free condition can beprovided by a nitrogen atmosphere or other inert gas atmosphere whereoxygen is absent or substantially absent. In addition, an oxygen-freecondition can be provided by placing the quantum dot formulation undervacuum.

According to one aspect, a borosilicate glass tube is filled underoxygen free conditions with a sparged and degassed quantum dotformulation. Accordingly, the quantum dot formulation within the tube issubstantially or completely free of oxygen. Glass capillaries aremaintained under conditions of suitable time, pressure and temperaturesufficient to dry the glass capillaries. A sparged and degassed quantumdot ink formulation is maintained in a quantum dot ink vessel undernitrogen. Dried capillaries with one end open are placed into a vacuumfill vessel with an open end down into quantum dot ink. The quantum dotink vessel is connected to the vacuum fill vessel via tubing and valvessuch that ink is able to flow from the quantum dot ink vessel to thevacuum fill vessel by applying pressure differentials. The pressurewithin the vacuum fill vessel is reduced to less than 200 mtorr and thenrepressurized with nitrogen. Quantum dot ink is admitted into the vacuumfill vessel by pressurization of the quantum dot ink vessel and thecapillaries are allowed to fill under oxygen free conditions.Alternatively, the vacuum fill vessel can be evacuated thereby drawingthe fluid up into the capillaries. After the capillaries are filled, thesystem is bled to atmospheric pressure. The exterior of the capillariesare then cleaned using toluene.

According to an additional embodiment with reference to FIG. 1, acapillary with one end sealed is connected to a filling or manifold headcapable of docking with the capillary and switching between vacuum andink fill. The capillary is evacuated by a vacuum having a vacuumcapability of less than 200 mTorr. Sparged and degassed quantum dot inkunder nitrogen pressure is then filled into the capillary. The quantumdot ink or formulation is under an oxygen-free condition, i.e., oxygenis substantially or completely absent. The lines and filling head areflushed with nitrogen. The capillary is held under an atmosphere ofnitrogen or vacuum and the end sealed, such as by melting the capillaryend and sealing, for example by a capillary sealing system. The ink maythen be cured in the capillary using UV light in a UV curing apparatusfor curing quantum dot ink.

In certain embodiments, for example, the quantum dot formulation withinthe vessel or tube or capillary completely or substantially lacks oxygenand can be cured with an H or D bulb emitting 900-1000 mjoules/cm² witha total dosage over about 1 to about 5 minutes. Alternatively, curingcan be accomplished using a Dymax 500EC UV Curing Flood system equippedwith a mercury UVB bulb. In such case, a lamp intensity (measured as 33mW/cm² at a distance of about 7″ from the lamp housing) can beeffective, with the capillary being cured for 10-15 seconds on each sidewhile being kept at a distance of 7 inches from the lamp housing. Aftercuring, the edges of the capillary can be sealed thereby providing acured quantum dot formulation under oxygen free conditions.

In certain embodiments relating to a temporary seal, sealing cancomprise using an optical adhesive or silicone to seal one or both endsor edges of the capillary. For example, a drop of optical adhesive canbe placed on each edge of the capillary and cured. An example of anoptical adhesive includes, but is not limited to, NOA-68T obtainablefrom Norland Optics. For example, a drop of such adhesive can be placedon each edge of the capillary and cured (e.g., for 20 seconds with aRolence Enterprise Model Q-Lux-UV lamp).

In certain embodiments, sealing can comprise using glass to seal one orboth ends or edges of the capillary. This can be done by brieflybringing a capillary filled with cured quantum dot ink into briefcontact with an oxygen/Mapp gas flame until the glass flows and sealsthe end. Oxygen-hydrogen flames may be used as well as any other mixedgas flame. The heat may also be supplied by laser eliminating the needfor an open flame. In certain embodiments, both ends of a capillaryfilled with uncured quantum dot ink under oxygen-free conditions can besealed, allowing the ink to then be photocured in the sealed capillary.

In certain embodiments, the capillary is hermetically sealed, i.e.,impervious to gases and moisture, thereby providing a sealed capillarywhere oxygen is substantially or completely absent.

In certain embodiments, the capillary is pseudo-hermetically sealed,i.e., at least partially impervious to gases and moisture.

Other suitable techniques can be used for sealing the ends or edges ofthe capillary.

In certain aspects and embodiments of the inventions taught herein, thetube including the cured quantum dot formulation (optical material) mayoptionally be exposed to light flux for a period of time sufficient toincrease the photoluminescent efficiency of the optical material.

In certain embodiments, the optical material is exposed to light andheat for a period of time sufficient to increase the photoluminescentefficiency of the optical material.

In preferred certain embodiments, the exposure to light or light andheat is continued for a period of time until the photoluminescentefficiency reaches a substantially constant value.

In one embodiment, for example, after the optic is filled with spargedand degassed quantum dot containing ink under oxygen free conditions,cured, and sealed (regardless of the order in which the curing andsealing steps are conducted), the optic is exposed, to 25-35 mW/cm²light flux with a wavelength in a range from about 365 nm to about 470nm, while at a temperature of in a range from about 25° C. to about 80°C., for a period of time sufficient to increase the photoluminescentefficiency of the ink. In one embodiment, for example, the light has awavelength of about 450 nm, the light flux is 30 mW/cm², the temperatureis 80° C., and the exposure time is 3 hours. Alternatively, the quantumdot containing ink can be cured within the tube before sealing one orboth ends of the tube.

According to one aspect of the present invention, a polymerizablecomposition including quantum dots is provided. Quantum dots may bepresent in the polymerizable composition in an amount from about 0.05%w/w to about 5.0% w/w. According to one aspect, the polymerizablecomposition is photopolymerizable. The polymerizable composition is inthe form of a fluid which can be placed within the tube underoxygen-free conditions and then one or both ends sealed with the tubebeing hermetically sealed to avoid oxygen being within the tube. Thepolymerizable composition is then subjected to light of sufficientintensity and for a period of time sufficient to polymerize thepolymerizable composition, and in one aspect, in the absence of oxygen.The period of time can range between about 10 seconds to about 6 minutesor between about 1 minute to about 6 minutes. According to oneembodiment, the period of time is sufficiently short to avoidagglomeration of the quantum dots prior to formation of a polymerizedmatrix. Agglomeration can result in FRET and subsequent loss ofphotoluminescent performance.

The polymerizable composition includes quantum dots in combination withone or more of a polymerizable composition. According to one aspect, thepolymerizable composition avoids, resists or inhibits yellowing when inthe form of a matrix, such as a polymerized matrix. A matrix in whichquantum dots are dispersed may be referred to as a host material. Hostmaterials include polymeric and non-polymeric materials that are atleast partially transparent, and preferably fully transparent, topreselected wavelengths of light.

According to an additional aspect, the polymerizable composition isselected so as to provide sufficient ductility to the polymerizedmatrix. Ductility is advantageous in relieving the stresses on the tubethat occur during polymer shrinkage when the polymer matrix is cured.Suitable polymerizable compositions act as solvents for the quantum dotsand so combinations of polymerizable compositions can be selected basedon solvent properties for various quantum dots.

Polymerizable compositions include monomers and oligomers and polymersand mixtures thereof. Exemplary monomers include lauryl methacrylate,norbornyl methacrylate, Ebecyl 150 (Cytec), CD590 (Cytec) and the like.Polymerizable materials can be present in the polymerizable formulationin an amount greater than 50 weight percent. Examples include amounts ina range greater than 50 to about 99.5 weight percent, greater than 50 toabout 98 weight percent, greater than 50 to about 95 weight percent,from about 80 to about 99.5 weight percent, from about 90 to about 99.95weight percent, from about 95 to about 99.95 weight percent. Otheramounts outside these examples may also be determined to be useful ordesirable.

Exemplary polymerizable compositions further include one or more of acrosslinking agent, a scattering agent, a rheology modifier, a filler,and a photoinitiator.

Suitable crosslinking agents include ethylene glycol dimethacrylate,Ebecyl 150 and the like. Crosslinking agents can be present in thepolymerizable formulation in an amount between about 0.5 wt % and about3.0 wt %. Crosslinking agents are generally added, for example in anamount of 1% w/w, to improve stability and strength of a polymer matrixwhich helps avoid cracking of the matrix due to shrinkage upon curing ofthe matrix.

Suitable scattering agents include TiO₂, alumina, barium sulfate, PTFE,barium titantate and the like. Scattering agents can be present in thepolymerizable formulation in an amount between about 0.05 wt % and about1.0 wt %. Scattering agents are generally added, for example in apreferred amount of about 0.15% w/w, to promote outcoupling of emittedlight.

Suitable rheology modifiers (thixotropes) include fumed silicacommercially available from Cabot Corporation such as TS-720 treatedfumed silica, treated silica commercially available from CabotCorporation such as TS720, TS500, TS530, TS610 and hydrophilic silicasuch as M5 and EHS commercially available from Cabot Corporation.Rheology modifiers can be present in the polymerizable formulation in anamount between about 5% w/w to about 12% w/w. Rheology modifiers orthixotropes act to lower the shrinkage of the matrix resin and helpprevent cracking. Hydrophobic rheology modifiers disperse more easilyand build viscosity at higher loadings allowing for more filler contentand less shrinkage to the point where the formulation becomes tooviscous to fill the tube. Rheology modifiers such as fumed silica alsoprovide higher EQE and help to prevent settling of TiO₂ on the surfaceof the tube before polymerization has taken place.

Suitable fillers include silica, fumed silica, precipitated silica,glass beads, PMMA beads and the like. Fillers can be present in thepolymerizable formulation in an amount between about 0.01% and about60%, about 0.01% and about 50%, about 0.01% and about 40%, about 0.01%and about 30%, about 0.01% and about 20% and any value or range inbetween whether overlapping or not.

Suitable photoinitiators include Irgacure 2022, KTO-46 (Lambert),Esacure 1 (Lambert) and the like. Photoinitiators can be present in thepolymerizable formulation in an amount between about 0.1% w/w to about5% w/w. Photoinitiators generally help to sensitize the polymerizablecomposition to UV light for photopolymerization. Thermal initiators suchas AIBN or peroxides can also be used.

Suitable inhibitor compounds which require oxygen to inhibit undesiredpolymerization or otherwise protect polymerizable compounds frompolymerization include those disclosed in Kice, J. Am. Chem. Soc., 1954,76(24), pp. 6274-6280 or Becker et al., Chem. Eng. Technol. 2006, 29,No. 10, 1227-1231 each of which are hereby incorporated by reference intheir entireties. Such inhibitor compounds include hydroquinone (HQ),hydroquinone monomethyl ether (MEHQ), phenothiazin,2,2′-azo-bis-isobutyronitrile, 2,2-diphenyl-1-picrylhydrazyl,benzoquinone, chloranil, furfurylidene malononitrile, benzhydrilidenemalononitrile, trinitrotoluene, m-dinitrobenzene, p-nitrotoluene,diphenylamine, BHT or other hindered phenols and the like.

According to additional aspects, quantum dots are nanometer sizedparticles that can have optical properties arising from quantumconfinement. The particular composition(s), structure, and/or size of aquantum dot can be selected to achieve the desired wavelength of lightto be emitted from the quantum dot upon stimulation with a particularexcitation source. In essence, quantum dots may be tuned to emit lightacross the visible spectrum by changing their size. See C. B. Murray, C.R. Kagan, and M. G. Bawendi, Annual Review of Material Sci., 2000, 30:545-610 hereby incorporated by reference in its entirety.

Quantum dots can have an average particle size in a range from about 1to about 1000 nanometers (nm), and preferably in a range from about 1 toabout 100 nm. In certain embodiments, quantum dots have an averageparticle size in a range from about 1 to about 20 nm (e.g., such asabout 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 nm).In certain embodiments, quantum dots have an average particle size in arange from about 1 to about 10 nm. Quantum dots can have an averagediameter less than about 150 Angstroms ({acute over (Å)}). In certainembodiments, quantum dots having an average diameter in a range fromabout 12 to about 150 {acute over (Å)} can be particularly desirable.However, depending upon the composition, structure, and desired emissionwavelength of the quantum dot, the average diameter may be outside ofthese ranges.

Preferably, a quantum dot comprises a semiconductor nanocrystal. Incertain embodiments, a semiconductor nanocrystal has an average particlesize in a range from about 1 to about 20 nm, and preferably from about 1to about 10 nm. However, depending upon the composition, structure, anddesired emission wavelength of the quantum dot, the average diameter maybe outside of these ranges.

A quantum dot can comprise one or more semiconductor materials.

Examples of semiconductor materials that can be included in a quantumdot (including, e.g., semiconductor nanocrystal) include, but are notlimited to, a Group IV element, a Group II-VI compound, a Group II-Vcompound, a Group III-VI compound, a Group III-V compound, a Group IV-VIcompound, a Group compound, a Group II-IV-VI compound, a Group II-IV-Vcompound, an alloy including any of the foregoing, and/or a mixtureincluding any of the foregoing, including ternary and quaternarymixtures or alloys. A non-limiting list of examples include ZnO, ZnS,ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, MgS, MgSe, GaAs, GaN, GaP, GaSe, GaSb,HgO, HgS, HgSe, HgTe, InAs, InN, InP, InSb, AlAs, AlN, AlP, AlSb, TlN,TlP, TlAs, TlSb, PbO, PbS, PbSe, PbTe, Ge, Si, an alloy including any ofthe foregoing, and/or a mixture including any of the foregoing,including ternary and quaternary mixtures or alloys.

In certain embodiments, quantum dots can comprise a core comprising oneor more semiconductor materials and a shell comprising one or moresemiconductor materials, wherein the shell is disposed over at least aportion, and preferably all, of the outer surface of the core. A quantumdot including a core and shell is also referred to as a “core/shell”structure.

For example, a quantum dot can include a core having the formula MX,where M is cadmium, zinc, magnesium, mercury, aluminum, gallium, indium,thallium, or mixtures thereof, and X is oxygen, sulfur, selenium,tellurium, nitrogen, phosphorus, arsenic, antimony, or mixtures thereof.Examples of materials suitable for use as quantum dot cores include, butare not limited to, ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, MgS,MgSe, GaAs, GaN, GaP, GaSe, GaSb, HgO, HgS, HgSe, HgTe, InAs, InN, InP,InSb, AlAs, AlN, AlP, AlSb, TlN, TlP, TlAs, TlSb, PbO, PbS, PbSe, PbTe,Ge, Si, an alloy including any of the foregoing, and/or a mixtureincluding any of the foregoing, including ternary and quaternarymixtures or alloys.

A shell can be a semiconductor material having a composition that is thesame as or different from the composition of the core. The shell cancomprise an overcoat including one or more semiconductor materials on asurface of the core. Examples of semiconductor materials that can beincluded in a shell include, but are not limited to, a Group IV element,a Group II-VI compound, a Group II-V compound, a Group III-VI compound,a Group III-V compound, a Group IV-VI compound, a Group I-III-VIcompound, a Group II-IV-VI compound, a Group II-IV-V compound, alloysincluding any of the foregoing, and/or mixtures including any of theforegoing, including ternary and quaternary mixtures or alloys. Examplesinclude, but are not limited to, ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe,CdTe, MgS, MgSe, GaAs, GaN, GaP, GaSe, GaSb, HgO, HgS, HgSe, HgTe, InAs,InN, InP, InSb, AlAs, AlN, AlP, AlSb, TlN, TlP, TlAs, TlSb, PbO, PbS,PbSe, PbTe, Ge, Si, an alloy including any of the foregoing, and/or amixture including any of the foregoing. For example, ZnS, ZnSe or CdSovercoatings can be grown on CdSe or CdTe semiconductor nanocrystals.

In a core/shell quantum dot, the shell or overcoating may comprise oneor more layers. The overcoating can comprise at least one semiconductormaterial which is the same as or different from the composition of thecore. Preferably, the overcoating has a thickness from about one toabout ten monolayers. An overcoating can also have a thickness greaterthan ten monolayers. In certain embodiments, more than one overcoatingcan be included on a core.

In certain embodiments, the surrounding “shell” material can have a bandgap greater than the band gap of the core material. In certain otherembodiments, the surrounding shell material can have a band gap lessthan the band gap of the core material.

In certain embodiments, the shell can be chosen so as to have an atomicspacing close to that of the “core” substrate. In certain otherembodiments, the shell and core materials can have the same crystalstructure.

Examples of quantum dot (e.g., semiconductor nanocrystal) (core)shellmaterials include, without limitation: red (e.g., (CdSe)CdZnS(core)shell), green (e.g., (CdZnSe)CdZnS (core)shell, etc.), and blue(e.g., (CdS)CdZnS (core)shell.

Quantum dots can have various shapes, including, but not limited to,sphere, rod, disk, other shapes, and mixtures of various shapedparticles.

One example of a method of manufacturing a quantum dot (including, forexample, but not limited to, a semiconductor nanocrystal) is a colloidalgrowth process. Colloidal growth occurs by injection an M donor and an Xdonor into a hot coordinating solvent. One example of a preferred methodfor preparing monodisperse quantum dots comprises pyrolysis oforganometallic reagents, such as dimethyl cadmium, injected into a hot,coordinating solvent. This permits discrete nucleation and results inthe controlled growth of macroscopic quantities of quantum dots. Theinjection produces a nucleus that can be grown in a controlled manner toform a quantum dot. The reaction mixture can be gently heated to growand anneal the quantum dot. Both the average size and the sizedistribution of the quantum dots in a sample are dependent on the growthtemperature. The growth temperature for maintaining steady growthincreases with increasing average crystal size. Resulting quantum dotsare members of a population of quantum dots. As a result of the discretenucleation and controlled growth, the population of quantum dots thatcan be obtained has a narrow, monodisperse distribution of diameters.The monodisperse distribution of diameters can also be referred to as asize. Preferably, a monodisperse population of particles includes apopulation of particles wherein at least about 60% of the particles inthe population fall within a specified particle size range. A populationof monodisperse particles preferably deviate less than 15% rms(root-mean-square) in diameter and more preferably less than 10% rms andmost preferably less than 5%.

An example of an overcoating process is described, for example, in U.S.Pat. No. 6,322,901. By adjusting the temperature of the reaction mixtureduring overcoating and monitoring the absorption spectrum of the core,overcoated materials having high emission quantum efficiencies andnarrow size distributions can be obtained.

The narrow size distribution of the quantum dots (including, e.g.,semiconductor nanocrystals) allows the possibility of light emission innarrow spectral widths. Monodisperse semiconductor nanocrystals havebeen described in detail in Murray et al. (J. Am. Chem. Soc., 115:8706(1993)); in the thesis of Christopher Murray, and “Synthesis andCharacterization of II-VI Quantum Dots and Their Assembly into 3-DQuantum Dot Superlattices”, Massachusetts Institute of Technology,September, 1995. The foregoing are hereby incorporated herein byreference in their entireties.

The process of controlled growth and annealing of the quantum dots inthe coordinating solvent that follows nucleation can also result inuniform surface derivatization and regular core structures. As the sizedistribution sharpens, the temperature can be raised to maintain steadygrowth. By adding more M donor or X donor, the growth period can beshortened. The M donor can be an inorganic compound, an organometalliccompound, or elemental metal. For example, an M donor can comprisecadmium, zinc, magnesium, mercury, aluminum, gallium, indium orthallium, and the X donor can comprise a compound capable of reactingwith the M donor to form a material with the general formula MX. The Xdonor can comprise a chalcogenide donor or a pnictide donor, such as aphosphine chalcogenide, a bis(silyl) chalcogenide, dioxygen, an ammoniumsalt, or a tris(silyl) pnictide. Suitable X donors include, for example,but are not limited to, dioxygen, bis(trimethylsilyl) selenide((TMS)₂Se), trialkyl phosphine selenides such as (tri-noctylphosphine)selenide (TOPSe) or (tri-n-butylphosphine) selenide (TBPSe), trialkylphosphine tellurides such as (tri-n-octylphosphine) telluride (TOPTe) orhexapropylphosphorustriamide telluride (HPPTTe),bis(trimethylsilyl)telluride ((TMS)₂Te), bis(trimethylsilyl)sulfide((TMS)₂S), a trialkyl phosphine sulfide such as (tri-noctylphosphine)sulfide (TOPS), an ammonium salt such as an ammonium halide (e.g.,NH₄Cl), tris(trimethylsilyl) phosphide ((TMS)₃P), tris(trimethylsilyl)arsenide ((TMS)₃As), or tris(trimethylsilyl) antimonide ((TMS)₃Sb). Incertain embodiments, the M donor and the X donor can be moieties withinthe same molecule.

A coordinating solvent can help control the growth of the quantum dot. Acoordinating solvent is a compound having a donor lone pair that, forexample, a lone electron pair available to coordinate to a surface ofthe growing quantum dot (including, e.g., a semiconductor nanocrystal).Solvent coordination can stabilize the growing quantum dot. Examples ofcoordinating solvents include alkyl phosphines, alkyl phosphine oxides,alkyl phosphonic acids, or alkyl phosphinic acids, however, othercoordinating solvents, such as pyridines, furans, and amines may also besuitable for the quantum dot (e.g., semiconductor nanocrystal)production. Additional examples of suitable coordinating solventsinclude pyridine, tri-n-octyl phosphine (TOP), tri-n-octyl phosphineoxide (TOPO) and trishydroxylpropylphosphine (tHPP), tributylphosphine,tri(dodecyl)phosphine, dibutyl-phosphite, tributyl phosphite,trioctadecyl phosphite, trilauryl phosphite, tris(tridecyl) phosphite,triisodecyl phosphite, bis(2-ethylhexyl)phosphate, tris(tridecyl)phosphate, hexadecylamine, oleylamine, octadecylamine,bis(2-ethylhexyl)amine, octylamine, dioctylamine, trioctylamine,dodecylamine/laurylamine, didodecylamine tridodecylamine,hexadecylamine, dioctadecylamine, trioctadecylamine, phenylphosphonicacid, hexylphosphonic acid, tetradecylphosphonic acid, octylphosphonicacid, octadecylphosphonic acid, propylenediphosphonic acid,phenylphosphonic acid, aminohexylphosphonic acid, dioctyl ether,diphenyl ether, methyl myristate, octyl octanoate, and hexyl octanoate.In certain embodiments, technical grade TOPO can be used.

In certain embodiments, quantum dots can alternatively be prepared withuse of non-coordinating solvent(s).

Size distribution during the growth stage of the reaction can beestimated by monitoring the absorption or emission line widths of theparticles. Modification of the reaction temperature in response tochanges in the absorption spectrum of the particles allows themaintenance of a sharp particle size distribution during growth.Reactants can be added to the nucleation solution during crystal growthto grow larger crystals. For example, for CdSe and CdTe, by stoppinggrowth at a particular semiconductor nanocrystal average diameter andchoosing the proper composition of the semiconducting material, theemission spectra of the semiconductor nanocrystals can be tunedcontinuously over the wavelength range of 300 nm to 5 microns, or from400 nm to 800 nm.

The particle size distribution of the quantum dots (including, e.g.,semiconductor nanocrystals) can be further refined by size selectiveprecipitation with a poor solvent for the quantum dots, such asmethanol/butanol. For example, quantum dots can be dispersed in asolution of 10% butanol in hexane. Methanol can be added dropwise tothis stirring solution until opalescence persists. Separation ofsupernatant and flocculate by centrifugation produces a precipitateenriched with the largest crystallites in the sample. This procedure canbe repeated until no further sharpening of the optical absorptionspectrum is noted. Size-selective precipitation can be carried out in avariety of solvent/nonsolvent pairs, including pyridine/hexane andchloroform/methanol. The size-selected quantum dot (e.g., semiconductornanocrystal) population preferably has no more than a 15% rms deviationfrom mean diameter, more preferably 10% rms deviation or less, and mostpreferably 5% rms deviation or less.

Semiconductor nanocrystals and other types of quantum dots preferablyhave ligands attached thereto. According to one aspect, quantum dotswithin the scope of the present invention include green CdSe quantumdots having oleic acid ligands and red CdSe quantum dots having oleicacid ligands. Alternatively, or in addition, octadecylphosphonic acid(“ODPA”) ligands may be used instead of oleic acid ligands. The ligandspromote solubility of the quantum dots in the polymerizable compositionwhich allows higher loadings without agglomeration which can lead to redshifting.

Ligands can be derived from a coordinating solvent that may be includedin the reaction mixture during the growth process.

Ligands can be added to the reaction mixture.

Ligands can be derived from a reagent or precursor included in thereaction mixture for synthesizing the quantum dots.

In certain embodiments, quantum dots can include more than one type ofligand attached to an outer surface.

A quantum dot surface that includes ligands derived from the growthprocess or otherwise can be modified by repeated exposure to an excessof a competing ligand group (including, e.g., but not limited to,coordinating group) to form an overlayer. For example, a dispersion ofthe capped quantum dots can be treated with a coordinating organiccompound, such as pyridine, to produce crystallites which dispersereadily in pyridine, methanol, and aromatics but no longer disperse inaliphatic solvents. Such a surface exchange process can be carried outwith any compound capable of coordinating to or bonding with the outersurface of the nanoparticle, including, for example, but not limited to,phosphines, thiols, amines and phosphates.

For example, a quantum dot can be exposed to short chain polymers whichexhibit an affinity for the surface and which terminate in a moietyhaving an affinity for a suspension or dispersion medium. Such affinityimproves the stability of the suspension and discourages flocculation ofthe quantum dot. Examples of additional ligands include fatty acidligands, long chain fatty acid ligands, alkyl phosphines, alkylphosphine oxides, alkyl phosphonic acids, or alkyl phosphinic acids,pyridines, furans, and amines. More specific examples include, but arenot limited to, pyridine, tri-n-octyl phosphine (TOP), tri-n-octylphosphine oxide (TOPO), tris-hydroxylpropylphosphine (tHPP) andoctadecylphosphonic acid (“ODPA”). Technical grade TOPO can be used.

Suitable coordinating ligands can be purchased commercially or preparedby ordinary synthetic organic techniques, for example, as described inJ. March, Advanced Organic Chemistry, which is incorporated herein byreference in its entirety.

The emission from a quantum dot capable of emitting light can be anarrow Gaussian emission band that can be tuned through the completewavelength range of the ultraviolet, visible, or infra-red regions ofthe spectrum by varying the size of the quantum dot, the composition ofthe quantum dot, or both. For example, a semiconductor nanocrystalcomprising CdSe can be tuned in the visible region; a semiconductornanocrystal comprising InAs can be tuned in the infra-red region. Thenarrow size distribution of a population of quantum dots capable ofemitting light can result in emission of light in a narrow spectralrange. The population can be monodisperse preferably exhibits less thana 15% rms (root-mean-square) deviation in diameter of such quantum dots,more preferably less than 10%, most preferably less than 5%. Spectralemissions in a narrow range of no greater than about 75 nm, preferablyno greater than about 60 nm, more preferably no greater than about 40nm, and most preferably no greater than about 30 nm full width at halfmax (FWHM) for such quantum dots that emit in the visible can beobserved. IR-emitting quantum dots can have a FWHM of no greater than150 nm, or no greater than 100 nm. Expressed in terms of the energy ofthe emission, the emission can have a FWHM of no greater than 0.05 eV,or no greater than 0.03 eV. The breadth of the emission decreases as thedispersity of the light-emitting quantum dot diameters decreases.

Quantum dots can have emission quantum efficiencies such as greater than10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%.

The narrow FWHM of quantum dots can result in saturated color emission.The broadly tunable, saturated color emission over the entire visiblespectrum of a single material system is unmatched by any class oforganic chromophores (see, for example, Dabbousi et al., J. Phys. Chem.101, 9463 (1997), which is incorporated by reference in its entirety). Amonodisperse population of quantum dots will emit light spanning anarrow range of wavelengths.

Useful quantum dots according to the present invention are those thatemit wavelengths characteristic of red light. In certain preferredembodiments, quantum dots capable of emitting red light emit lighthaving a peak center wavelength in a range from about 615 nm to about635 nm, and any wavelength or range in between whether overlapping ornot. For example, the quantum dots can be capable or emitting red lighthaving a peak center wavelength of about 635 nm, about 630 nm, of about625 nm, of about 620 nm, of about 615 nm.

Useful quantum dots according to the present invention are also thosethat emit wavelength characteristic of green light. In certain preferredembodiments, quantum dots capable of emitting green light emit lighthaving a peak center wavelength in a range from about 520 nm to about545 nm, and any wavelength or range in between whether overlapping ornot. For example, the quantum dots can be capable or emitting greenlight having a peak center wavelength of about 520 nm, of about 525 nm,of about 535 nm, of about 540 nm or of about 540 nm.

According to further aspects of the present invention, the quantum dotsexhibit a narrow emission profile in the range of between about 23 nmand about 60 nm at full width half maximum (FWHM). The narrow emissionprofile of quantum dots of the present invention allows the tuning ofthe quantum dots and mixtures of quantum dots to emit saturated colorsthereby increasing color gamut and power efficiency beyond that ofconventional LED lighting displays. According to one aspect, greenquantum dots designed to emit a predominant wavelength of, for example,about 523 nm and having an emission profile with a FWHM of about, forexample, 37 nm are combined, mixed or otherwise used in combination withred quantum dots designed to emit a predominant wavelength of about, forexample, 617 nm and having an emission profile with a FWHM of about, forexample 32 nm. Such combinations can be stimulated by blue light tocreate trichromatic white light.

Quantum dots in accordance with the present invention can be included invarious formulations depending upon the desired utility. According toone aspect, quantum dots are included in flowable formulations orliquids to be included, for example, into clear vessels, such as tubes,which are to be exposed to light. Such formulations can include variousamounts of one or more type of quantum dots and one or more hostmaterials. Such formulations can further include one or more scatterers.Other optional additives or ingredients can also be included in aformulation. In certain embodiments, a formulation can further includeone or more photo initiators. One of skill in the art will readilyrecognize from the present invention that additional ingredients can beincluded depending upon the particular intended application for thequantum dots.

An optical material or formulation within the scope of the invention mayinclude a host material, such as can be included in an optical componentdescribed herein, which may be present in an amount from about 50 weightpercent and about 99.5 weight percent, and any weight percent in betweenwhether overlapping or not. In certain embodiment, a host material maybe present in an amount from about 80 to about 99.5 weight percent.Examples of specific useful host materials include, but are not limitedto, polymers, oligomers, monomers, resins, binders, glasses, metaloxides, and other nonpolymeric materials. Preferred host materialsinclude polymeric and non-polymeric materials that are at leastpartially transparent, and preferably fully transparent, to preselectedwavelengths of light. In certain embodiments, the preselectedwavelengths can include wavelengths of light in the visible (e.g.,400-700 nm) region of the electromagnetic spectrum. Preferred hostmaterials include cross-linked polymers and solvent-cast polymers.Examples of other preferred host materials include, but are not limitedto, glass or a transparent resin. In particular, a resin such as anon-curable resin, heat-curable resin, or photocurable resin is suitablyused from the viewpoint of processability. Specific examples of such aresin, in the form of either an oligomer or a polymer, include, but arenot limited to, a melamine resin, a phenol resin, an alkyl resin, anepoxy resin, a polyurethane resin, a maleic resin, a polyamide resin,polymethyl methacrylate, polyacrylate, polycarbonate, polyvinyl alcohol,polyvinylpyrrolidone, hydroxyethylcellulose, carboxymethylcellulose,copolymers containing monomers or oligomers forming these resins, andthe like. Other suitable host materials can be identified by persons ofordinary skill in the relevant art.

Host materials can also comprise silicone materials. Suitable hostmaterials comprising silicone materials can be identified by persons ofordinary skill in the relevant art.

In certain embodiments and aspects of the inventions contemplated bythis invention, a host material comprises a photocurable resin. Aphotocurable resin, may be a preferred host material in certainembodiments, e.g., in embodiments in which the composition is to bepatterned. As a photo-curable resin, a photo-polymerizable resin such asan acrylic acid or methacrylic acid based resin containing a reactivevinyl group, a photo-crosslinkable resin which generally contains aphoto-sensitizer, such as polyvinyl cinnamate, benzophenone, or the likemay be used. A heat-curable resin may be used when the photo-sensitizeris not used. These resins may be used individually or in combination oftwo or more.

In certain embodiments, a host material can comprise a solvent-castresin. A polymer such as a polyurethane resin, a maleic resin, apolyamide resin, polymethyl methacrylate, polyacrylate, polycarbonate,polyvinyl alcohol, polyvinylpyrrolidone, hydroxyethylcellulose,carboxymethylcellulose, copolymers containing monomers or oligomersforming these resins, and the like can be dissolved in solvents known tothose skilled in the art. Upon evaporation of the solvent, the resinforms a solid host material for the semiconductor nanoparticles.

In certain embodiments, acrylate monomers and/or acrylate oligomerswhich are commercially available from Radcure and Sartomer can bepreferred.

Quantum dots can be encapsulated. Nonlimiting examples of encapsulationmaterials, related methods, and other information that may be useful aredescribed in International Application No. PCT/US2009/01372 of Linton,filed 4 Mar. 2009 entitled “Particles Including Nanoparticles, UsesThereof, And Methods” and U.S. Patent Application No. 61/240,932 of Nicket, al., filed 9 Sep. 2009 entitled “Particles Including Nanoparticles,Uses Thereof, And Methods”, each of the foregoing being herebyincorporated herein by reference in its entirety.

The total amount of quantum dots included in an optical material, suchas a host material for example a polymer matrix, within the scope of theinvention is preferably in a range from about 0.05 weight percent toabout 5 weight percent, and more preferably in a range from about 0.1weight percent to about 5 weight percent and any value or range inbetween whether overlapping or not. The amount of quantum dots includedin an optical material can vary within such range depending upon theapplication and the form in which the quantum dots are included (e.g.,film, optics (e.g., capillary), encapsulated film, etc.), which can bechosen based on the particular end application. For instance, when anoptic material is used in a thicker capillary with a longer pathlength(e.g., such as in BLUs for large screen television applications), theconcentration of quantum dots can be closer to 0.5%. When an opticalmaterial is used in a thinner capillary with a shorter pathlength (e.g.,such as in BLUs for mobile or hand-held applications), the concentrationof quantum dots can be closer to 5%.

The ratio of quantum dots used in an optical material is determined bythe emission peaks of the quantum dots used. For example, when quantumdots capable of emitting green light having a peak center wavelength ina range from about 514 nm to about 545 nm, and any wavelength in betweenwhether overlapping or not, and quantum dots capable of emitting redlight having a peak center wavelength in a range from about 615 nm toabout 640 nm, and any wavelength in between whether overlapping or not,are used in an optical material, the ratio of the weight percentgreen-emitting quantum dots to the weight percent of red-emittingquantum dots can be in a range from about 12:1 to about 1:1, and anyratio in between whether overlapping or not.

The above ratio of weight percent green-emitting quantum dots to weightpercent red-emitting quantum dots in an optical material canalternatively be presented as a molar ratio. For example, the aboveweight percent ratio of green to red quantum dots range can correspondto a green to red quantum dot molar ratio in a range from about 24.75 to1 to about 5.5 to 1, and any ratio in between whether overlapping ornot.

The ratio of the blue to green to red light output intensity in whitetrichromatic light emitted by a quantum dot containing BLU describedherein including blue-emitting solid state inorganic semiconductor lightemitting devices (having blue light with a peak center wavelength in arange from about 450 nm to about 460 nm, and any wavelength in betweenwhether overlapping or not), and an optical material including mixturesof green-emitting quantum dots and red-emitting quantum dots within theabove range of weight percent ratios can vary within the range. Forexample, the ratio of blue to green light output intensity therefor canbe in a range from about 0.75 to about 4 and the ratio of green to redlight output intensity therefor can be in a range from about 0.75 toabout 2.0. In certain embodiments, for example, the ratio of blue togreen light output intensity can be in a range from about 1.0 to about2.5 and the ratio of green to red light output intensity can be in arange from about 0.9 to about 1.3.

Scatterers, also referred to as scattering agents, within the scope ofthe invention may be present, for example, in an amount of between about0.01 weight percent and about 1 weight percent. Amounts of scatterersoutside such range may also be useful. Examples of light scatterers(also referred to herein as scatterers or light scattering particles)that can be used in the embodiments and aspects of the inventionsdescribed herein, include, without limitation, metal or metal oxideparticles, air bubbles, and glass and polymeric beads (solid or hollow).Other light scatterers can be readily identified by those of ordinaryskill in the art. In certain embodiments, scatterers have a sphericalshape. Preferred examples of scattering particles include, but are notlimited to, TiO₂, SiO₂, BaTiO₃, BaSO₄, and ZnO. Particles of othermaterials that are non-reactive with the host material and that canincrease the absorption pathlength of the excitation light in the hostmaterial can be used. In certain embodiments, light scatterers may havea high index of refraction (e.g., TiO₂, BaSO₄, etc) or a low index ofrefraction (gas bubbles).

Selection of the size and size distribution of the scatterers is readilydeterminable by those of ordinary skill in the art. The size and sizedistribution can be based upon the refractive index mismatch of thescattering particle and the host material in which the light scatterersare to be dispersed, and the preselected wavelength(s) to be scatteredaccording to Rayleigh scattering theory. The surface of the scatteringparticle may further be treated to improve dispersability and stabilityin the host material. In one embodiment, the scattering particlecomprises TiO₂ (R902+ from DuPont) of 0.2 μm particle size, in aconcentration in a range from about 0.01 to about 1% by weight.

The amount of scatterers in a formulation is useful in applicationswhere the ink is contained in a clear vessel having edges to limitlosses due the total internal reflection. The amount of the scatterersmay be altered relative to the amount of quantum dots used in theformulation. For example, when the amount of the scatter is increased,the amount of quantum dots may be decreased.

Examples of thixotropes which may be included in a quantum dotformulation, also referred to as rheology modifiers, include, but arenot limited to, fumed metal oxides (e.g., fumed silica which can besurface treated or untreated (such as Cab-O—Sil™ fumed silica productsavailable from Cabot Corporation), fumed metal oxide gels (e.g., asilica gel). An optical material can include an amount of thixotrope ina range from about 5 to about 12 weight percent. Other amounts outsidethe range may also be determined to be useful or desirable.

In certain embodiments, a formulation including quantum dots and a hostmaterial can be formed from an ink comprising quantum dots and a liquidvehicle, wherein the liquid vehicle comprises a composition includingone or more functional groups that are capable of being cross-linked.The functional units can be cross-linked, for example, by UV treatment,thermal treatment, or another cross-linking technique readilyascertainable by a person of ordinary skill in a relevant art. Incertain embodiments, the composition including one or more functionalgroups that are capable of being cross-linked can be the liquid vehicleitself. In certain embodiments, it can be a co-solvent. In certainembodiments, it can be a component of a mixture with the liquid vehicle.

One particular example of a preferred method of making an ink is asfollows. A solution including quantum dots having the desired emissioncharacteristics well dispersed in an organic solvent is concentrated tothe consistency of a wax by first stripping off the solvent undernitrogen/vacuum until a quantum dot containing residue with the desiredconsistency is obtained. The desired resin monomer is then added undernitrogen conditions, until the desired monomer to quantum dot ratio isachieved. This mixture is then vortex mixed under oxygen free conditionsuntil the quantum dots are well dispersed. The final components of theresin are then added to the quantum dot dispersion, and are thensonicated mixed to ensure a fine dispersion.

According to aspects of the present disclosure, the quantum dotformulation is then subjected to an oxygen-containing atmosphere for aperiod of time, such as a storage time or a transportation time asdescribed herein. When the quantum dot formulation is desired to beused, the quantum dot formulation is sparged and/or degassed asdescribed herein. The sparged and/or degassed quantum dot formulation isthen introduced into a vessel or tube or container for further use anoptical component, or is otherwise introduced into materials orformulations for making other quantum light materials such as films.

A tube or capillary comprising an optical material prepared from suchsparged and degassed quantum dot ink can be prepared by then introducingthe ink into the tube via a wide variety of methods, and then UV curedunder intense illumination for some number of seconds for a completecure. According to one aspect, the ink is introduced into the tube underoxygen-free conditions.

In certain aspects and embodiments of the inventions taught herein, theoptic including the cured quantum dot containing ink is exposed to lightflux for a period of time sufficient to increase the photoluminescentefficiency of the optical material.

In certain embodiments, the optical material is exposed to light andheat for a period of time sufficient to increase the photoluminescentefficiency of the optical material.

In preferred certain embodiments, the exposure to light or light andheat is continued for a period of time until the photoluminescentefficiency reaches a substantially constant value.

In one embodiment, for example, after the optic, i.e. tube or capillary,is filled with quantum dot containing ink under oxygen free conditions,cured, and sealed (regardless of the order in which the curing andsealing steps are conducted) to produce an optic having no orsubstantially no oxygen within the sealed optic, the optic is exposed to25-35 mW/cm² light flux with a wavelength in a range from about 365 nmto about 470 nm while at a temperature of in a range from about 25 to80° C., for a period of time sufficient to increase the photoluminescentefficiency of the ink. In one embodiment, for example, the light has awavelength of about 450 nm, the light flux is 30 mW/cm², the temperatureis 80° C., and the exposure time is 3 hours.

Additional information that may be useful in connection with the presentdisclosure and the inventions described herein is included inInternational Application No. PCT/US2009/002796 of Coe-Sullivan et al,filed 6 May 2009, entitled “Optical Components, Systems Including AnOptical Component, And Devices”; International Application No.PCT/US2009/002789 of Coe-Sullivan et al, filed 6 May 2009, entitled:“Solid State Lighting Devices Including Quantum Confined SemiconductorNanoparticles, An Optical Component For A Solid State Light Device, AndMethods”; International Application No. PCT/US2010/32859 of Modi et al,filed 28 Apr. 2010 entitled “Optical Materials, Optical Components, AndMethods”; International Application No. PCT/US2010/032799 of Modi et al,filed 28 Apr. 2010 entitled “Optical Materials, Optical Components,Devices, And Methods”; International Application No. PCT/US2011/047284of Sadasivan et al, filed 10 Aug. 2011 entitled “Quantum Dot BasedLighting”; International Application No. PCT/US2008/007901 of Linton etal, filed 25 Jun. 2008 entitled “Compositions And Methods IncludingDepositing Nanomaterial”; U.S. patent application Ser. No. 12/283,609 ofCoe-Sullivan et al, filed 12 Sep. 2008 entitled “Compositions, OpticalComponent, System Including An Optical Component, Devices, And OtherProducts”; International Application No. PCT/US2008/10651 of Breen etal, filed 12 Sep. 2008 entitled “Functionalized Nanoparticles AndMethod”; U.S. Pat. No. 6,600,175 of Baretz, et al., issued Jul. 29,2003, entitled “Solid State White Light Emitter And Display Using Same”;and U.S. Pat. No. 6,608,332 of Shimizu, et al., issued Aug. 19, 2003,entitled “Light Emitting Device and Display”; each of the foregoingbeing hereby incorporated herein by reference in its entirety.

LEDs within the scope of the present invention include any conventionalLED such as those commercially available from Citizen, Nichia, Osram,Cree, or Lumileds. Useful light emitted from LEDs includes white light,off white light, blue light, green light and any other light emittedfrom an LED.

Example I Preparation of Semiconductor Nanocrystals Capable of EmittingRed Light

Synthesis of CdSe Seed Cores:

262.5 mmol of cadmium acetate was dissolved in 3.826 mol oftri-n-octylphosphine at 100° C. in a 3 L 3-neck round-bottom flask andthen dried and degassed for one hour. 4.655 mol of trioctylphosphineoxide and 599.16 mmol of octadecylphosphonic acid were added to a 5 Lstainless steel reactor and dried and degassed at 140° C. for one hour.After degassing, the Cd solution was added to the reactor containing theoxide/acid and the mixture was heated to 310° C. under nitrogen. Oncethe temperature reached 310° C., the heating mantle is removed from thereactor and 731 mL of 1.5 M diisobutylphosphine selenide (DIBP-Se)(900.2 mmol Se) in 1-Dodecyl-2-pyrrolidinone (NDP) was then rapidlyinjected. The reactor is then immediately submerged in partially frozen(via liquid nitrogen) squalane bath rapidly reducing the temperature ofthe reaction to below 100° C. The first absorption peak of thenanocrystals was 480 nm. The CdSe cores were precipitated out of thegrowth solution inside a nitrogen atmosphere glovebox by adding a 3:1mixture of methanol and isopropanol. After removal of themethanol/isopropanol mixture, the isolated cores were then dissolved inhexane and used to make core-shell materials. The isolated materialspecifications were as follows: Optical Density @ 350 nm=2.83; Abs=481nm; Emission=510 nm; FWHM=40 nm; Total Volume=1.9 L of hexane.

Growth of CdSe Cores:

A 1 L glass reactor was charged with 320 mL of 1-octadecene (ODE) anddegassed at 120° C. for 15 minutes under vacuum. The reactor was thenbackfilled with N₂ and the temperature set to 60° C. 120 mL of the CdSeseed core above was injected into the reactor and the hexanes wereremoved under reduced pressure until the vacuum gauge reading was <500mTorr. The temperature of the reaction mixture was then set to 240° C.Meanwhile, two 50 mL syringes were loaded with 80 mL of cadmium oleatein TOP (0.5 M conc.) solution and another two syringes were loaded with80 mL of di-iso-butylphosphine selenide (DiBP-Se) in TOP (0.5 M conc.).Once the reaction mixture reached 240° C., the Cd oleate and DiBP-Sesolutions were infused into the reactor at a rate of 35 mL/hr. The lexcitonic absorption feature of the CdSe cores was monitored duringinfusion and the reaction was stopped at ˜60 minutes when the absorptionfeature was 569 nm. The resulting CdSe cores were then ready for use asis in this growth solution for overcoating.

Synthesis of CdSe/ZnS/CdZnS Core-Shell Nanocrystals:

115 mL of the CdSe core above with a first absorbance peak at 569 nm wasmixed in a 1 L reaction vessel with 1-octadecene (45 mL), and Zn(Oleate)(0.5 M in TOP, 26 mL). The reaction vessel was heated to 120° C. andvacuum was applied for 15 min. The reaction vessel was then back-filledwith nitrogen and heated to 310° C. The temperature was ramped, between1° C./5 seconds and 1° C./15 seconds. Once the vessel reached 300° C.,octanethiol (11.4 mL) was swiftly injected and a timer started. Once thetimer reached 6 min., one syringe containing zinc oleate (0.5 M in TOP,50 mL) and cadmium oleate (1 M in TOP, 41 mL), and another syringecontaining octanethiol (42.2 mL) were swiftly injected. Once the timerreached 40 min., the heating mantle was dropped and the reaction cooledby subjecting the vessel to a cool air flow. The final material wasprecipitated via the addition of butanol and methanol (4:1 ratio),centrifuged at 3000 RCF for 5 min, and the pellet redispersed intohexanes. The sample is then precipitated once more via the addition ofbutanol and methanol (3:1 ratio), centrifuged, and dispersed intotoluene for storage (616 nm emission, 25 nm FWHM, 80% QY, and 94% EQE infilm).

Example II Preparation of Semiconductor Nanocrystals Capable of EmittingGreen Light

Synthesis of CdSe Cores:

262.5 mmol of cadmium acetate was dissolved in 3.826 mol oftri-n-octylphosphine at 100° C. in a 3 L 3-neck round-bottom flask andthen dried and degassed for one hour. 4.655 mol of trioctylphosphineoxide and 599.16 mmol of octadecylphosphonic acid were added to a 5 Lstainless steel reactor and dried and degassed at 140° C. for one hour.After degassing, the Cd solution was added to the reactor containing theoxide/acid and the mixture was heated to 310° C. under nitrogen. Oncethe temperature reached 310° C., the heating mantle was removed from thereactor and 731 mL of 1.5 M diisobutylphosphine selenide (DIBP-Se)(900.2 mmol Se) in 1-Dodecyl-2-pyrrolidinone (NDP) was then rapidlyinjected. The reactor was then immediately submerged in a partiallyfrozen (via liquid nitrogen) squalane bath rapidly reducing thetemperature of the reaction to below 100° C. The first absorption peakof the nanocrystals was 487 nm. The CdSe cores were precipitated out ofthe growth solution inside a nitrogen atmosphere glovebox by adding a3:1 mixture of methanol and isopropanol. The isolated cores were thendissolved in hexane and used to make core-shell materials. The isolatedmaterial specifications were as follows: Optical Density @ 350 nm=1.62;Abs=486 nm; Emission=509 nm; FWHM=38 nm; Total Volume=1.82 L of hexane.

Synthesis of CdSe/ZnS/CdZnS Core-Shell Nanocrystals:

335 mL of 1-octadecene (ODE), 12.55 g of zinc acetate, and 38 mL ofoleic acid were loaded into a 1 L glass reactor and degassed at 100° C.for 1 hour. In a 1 L 3-neck flask, 100 mL of ODE was degassed at 120° C.for 1 hour. After degassing, the temperature of the flask was reduced to65° C. and then 23.08 mmol of CdSe cores from the procedure above (275mL) were blended into the 100 mL of degassed ODE and the hexane wasremoved under reduced pressure. The temperature of the reactor was thenraised to 310° C. In a glove box, the core/ODE solution and 40 mL ofoctanethiol were added to a 180 mL container. In a 600 mL container, 151mL of 0.5 M Zn Oleate in TOP, 37 mL of 1.0 M Cd Oleate in TOP, and 97 mLof 2 M TOP-S were added. Once the temperature of the reactor hit 310°C., the ODE/QD cores/Octanethiol mixture was injected into the reactorand allowed to react for 30 min at 300° C. After this reaction period,the Zn Oleate/Cd Oleate/TOP-S mixture was injected to the reactor andthe reaction was allowed to continue for an additional 30 minutes atwhich point the mixture was cooled to room temperature. The resultingcore-shell material was precipitated out of the growth solution inside anitrogen atmosphere glovebox by adding a 2:1 mixture of butanol andmethanol. The isolated quantum dots (QDs) were then dissolved in tolueneand precipitated a second time using 2:3 butanol:methanol. The QDs werefinally dispersed in toluene. The isolated material specifications wereas follows: Optical Density @ 450 nm (100 Fold Dilution)=0.32; Abs=501nm; Emission=518 nm; FWHM=38 nm; Solution QY=60%; Film EQE=93%.

Example III Preparation of Polymerizable Formulation Including QuantumDots

A clean, dry Schlenk flask equipped with a magnetic stir bar and rubberseptum was charged with, lauryl methacrylate (LMA) (Aldrich Chemical,96%), dodecanediol diacrylate (D3DMA) as well as any additive(s)indicated for the particular example. If additives were used, dispersionin the monomer was assisted by placing the suspension in a sonic bathfor 4 minutes and heating gently with a heat gun until no more solidwill dissolve. The solution was inerted using a vacuum manifold anddegassed in a standard protocol by freeze-pump-thawing the mixture threetimes successively using liquid nitrogen. The thawed solution is finallyplaced under nitrogen and labeled “monomer solution”.

Separately, a clean, dry Schlenk flask equipped with a magnetic stir barand rubber septum was charged with treated fumed silica (TS-720, CabotCorp), titanium dioxide (R902+, DuPont Corp.) and inerted undernitrogen. To this is added toluene (dry and oxygen free). The mixture isplaced in an ultrasonic bath for 10 minutes and then stirred undernitrogen. This is labeled “metal oxide slurry”.

Separately, a clean, dry Schlenk flask equipped with a magnetic stir barand rubber septum was inerted under nitrogen. The flask was then chargedwith a green quantum dot solution in toluene, red quantum dot solutionin toluene and additional toluene via syringe and allowed to stir for 5minutes. Over 6 minutes, the contents of the “monomer solution flask”were added via syringe and stirred for an additional five minutes. Thecontents of the “metal oxide slurry” flask were next added over 5minutes via cannula and rinsed over with the aid of a minimum amount ofadditional toluene.

The stirred flask was then placed in a warm water bath (<60° C.),covered with aluminum foil to protect from light and placed under avacuum to remove all of the toluene to a system pressure of <200 mtorr.After solvent removal was completed, slurry was removed from heat and,with stirring, Irgacure 2022 photoinitiator (BASF), withoutpurification, was added via syringe and allowed to stir for 5 minutes.The final ink was then ready for transfer to a fill station.

Example IV Light Emission Characteristics from Quantum Dot FormulationsExposed to Air, Sparged and Degassed

A quantum dot formulation using the method of Example III was preparedhaving the following composition: 0.5% green quantum dots, 0.2% redquantum dots, 0.2% TiO₂, 5.0% TOPO, 10.0% silica, 69.1% LMA, 14.0% D3MA(dodecyldimethacrylate) and 1.0% Irgacure 2022. A sample of quantum dotformulation was exposed to air for 11 days. The sample was kept in thedark to prevent any polymerization. After 11 days, about 15 ml of thesample was placed in a Schlenk flask and sparged with argon gas for 15min. The sparging was accomplished via a needle inserted below theliquid surface that transferred argon from a source to the liquid. Thegas flow rate was adjusted to impart a vigorous water boiling appearanceto the liquid while sparging. A stir bar was also used to keep theliquid mixed during sparging. After 15 min, the argon flow was stoppedand vacuum was applied to the liquid to completely de-gas it prior tofilling it in a glass tube. The sparged and degassed quantum dotformulation was introduced into a tube with a seal at one end. Theliquid was filled into the tube by completely evacuating the tube firstusing vacuum, then dipping the open end of the tube into the liquid, andthen using pressure on the liquid surface to move it into the tube. Oncethe tube was filled, the second end was sealed, and the entire tube wasexposed to UV light to polymerize the monomer.

The control (t=0) sample tube was filled in a similar manner, exceptthat the control was a quantum dot formulation of the same compositionthat was not exposed to air. Two control and two sparged sample tubeswere then exposed to a high light flux using a 400 mW blue LED tester,which resulted in polymer temperatures of about 120° C. The performanceof both capillaries was monitored with time on the tester using aninline color sensor. The performance (lumens, CIE_(x), CIE_(y)) of bothsets of samples are plotted in FIGS. 2, 3 and 4 which show that thesparged samples behaved similar to the control samples.

As used herein, the singular forms “a”, “an” and “the” include pluralunless the context clearly dictates otherwise. Thus, for example,reference to an emissive material includes reference to one or more ofsuch materials.

Applicants specifically incorporate the entire contents of all citedreferences in this disclosure. Further, when an amount, concentration,or other value or parameter is given as either a range, preferred range,or a list of upper preferable values and lower preferable values, thisis to be understood as specifically disclosing all ranges formed fromany pair of any upper range limit or preferred value and any lower rangelimit or preferred value, regardless of whether ranges are separatelydisclosed. Where a range of numerical values is recited herein, unlessotherwise stated, the range is intended to include the endpointsthereof, and all integers and fractions within the range. It is notintended that the scope of the invention be limited to the specificvalues recited when defining a range.

Other embodiments of the present invention will be apparent to thoseskilled in the art from consideration of the present specification andpractice of the present invention disclosed herein. It is intended thatthe present specification and examples be considered as exemplary onlywith a true scope and spirit of the invention being indicated by thefollowing claims and equivalents thereof.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

1. A method of processing a quantum dot formulation including oxygencomprising displacing the oxygen with an inert gas; and degassing thequantum dot formulation.
 2. The method of claim 1 wherein the inert gasis introduced into the quantum dot formulation to the extent sufficientto remove substantially all oxygen from the quantum dot formulation. 3.The method of claim 1 wherein the displacing step comprises sparging thequantum dot formulation with an inert gas.
 4. The method of claim 1wherein the processed quantum dot formulation includes substantially nooxygen.
 5. The method of claim 1 wherein the inert gas is nitrogen,helium, neon, argon, krypton, xenon or radon.
 6. (canceled)
 7. Themethod of claim 1 wherein the quantum dot formulation is degassed to theextent sufficient to remove substantially all gas from the quantum dotformulation.
 8. The method of claim 1 wherein the degassed quantum dotformulation includes substantially no gas.
 9. The method of claim 1wherein the quantum dot formulation comprises quantum dots and anunpolymerized polymerizable component.
 10. The method of claim 1 whereinthe quantum dot formulation includes an inhibitor compound.
 11. Themethod of claim 1 further comprising the step of introducing theprocessed quantum dot formulation into a tube.
 12. The method of claim 1further comprising the step of introducing the processed quantum dotformulation into a vessel.
 13. The method of claim 11 wherein the tubeis a capillary.
 14. The method of claim 11 wherein the tube ishermetically sealed and wherein oxygen is absent or substantially absentfrom within the tube.
 15. The method of claim 12 wherein the vessel ishermetically sealed and wherein oxygen is absent or substantially absentfrom within the vessel.
 16. The method of claim 11 further comprisingthe step of polymerizing the quantum dot formulation within the tube.17-22. (canceled)
 23. A method of processing a quantum dot formulationincluding dissolved oxygen comprising introducing an inert gas into thequantum dot formulation for a time period sufficient to removesubstantially all oxygen from the quantum dot formulation; subjectingthe quantum dot formulation to vacuum; and degassing the quantum dotformulation to remove substantially all dissolved gas from the quantumdot formulation. 24-34. (canceled)
 35. A closed container including aquantum dot formulation and oxygen.
 36. The container of claim 35wherein the quantum dot formulation comprises quantum dots and anunpolymerized polymerizable component.
 37. The container of claim 35wherein the quantum dot formulation further includes an inhibitorcompound.
 38. The container of claim 35 wherein the container is opaqueto light. 39-41. (canceled)